Varying redline ...?

[Grumpy Goat]

Is it normal for the redline to display 4000, then 8000 as the oil warms then 9000 when the oil reaches safe operating temp. ?
I figured it went from 4,000 to 9,000.
Seems odd to have the redline jump from 4,000 to 8,000, then have a small jump to 9,000.
Like I mentioned before I rarely look at the tach bar scale.

Oh, mine does not jump from 4000 to 8000 ... it just starts at about 4000 and gradually progresses up to 9000 rpm.

This behaviour I am describing is after it has warmed up to the normal 9000 rpm limit, it periodically drops down to 8000 rpm, and then may also jump back up to 9000 rpm. All while the engine and ambient conditions are more or less constant.

Like Mike and Bob have suggested, I am suspecting a sensor acting up.